Age is of great significance to understanding the causes of landslide instability and movement, and therefore, it is important to know when conducting a hazard assessment. To date, no detailed and comprehensive determination of the age of the Mahu giant landslide has been conducted. The Mahu giant landslide is located in the lower reaches of the Jinsha River and has a volume of 2.38 km³ and a maximum elevation difference of 1080 m, making it the largest subaerial landslide found to date in China. In this study, we report the age of the landslide based on ³⁶Cl exposure dating. Ten cosmogenic nuclide samples were collected from boulders on the landslide deposits and the bedrock on the landslide's scarp, and eight valid ages were derived in the range of 11.63 ± 0.96 to 29.14 ± 1.81 ka. Based on the lithologies and ages of the landslide's scarp and the deposits, the landslide is concluded to have been formed by two major events, with error weighted mean ages of 14.75 and 25.21 ka. The age results for the Mahu landslide obtained in this study provide a basis for understanding the causes of the Mahu landslide. Moreover, this case study indicates that the regional fault activity and earthquake risk can be analyzed from the perspective of landslide science.